Transportation costs associated with a hydrocarbon fluid, for example, gasoline or other hydrocarbon resources, may account for an increased percentage of the overall fuel cost. To reduce transportation costs associated with a hydrocarbon fluid, several methods for distributing the hydrocarbon fluid in bulk have been used. For example, container or tanker ships or vehicles may be used to transport a relatively large amount of hydrocarbon fluids. Another method for transporting a hydrocarbon fluid may be a hydrocarbon fluid pipeline, for example.
One particular hydrocarbon transport pipeline is the Trans Alaska Pipeline System (TAPS). The Trans Alaska Pipeline System includes about 800 miles (1,287 km) of hydrocarbon fluid pipeline with a diameter of 48 inches (122 cm) that conveys oil from Prudhoe Bay, to Valdez, Ak. and transports primarily crude oil.
A hydrocarbon fluid pipeline in a particularly cold environment, such as, for example, Alaska, may be subject to increased operational issues that may result from heat loss. Additionally, as flow rates in a hydrocarbon fluid pipeline decrease, temperature and turbulence decreases.
Some operational issues associated with reduced flow rates or reduced temperatures may include wax precipitation and deposition that forms at temperatures below 75° F., and water drop out, which may lead to increased corrosion and increased ice formation. Other operational issues may include geotechnical issues, for example, formation of ice in buried sections of pipeline, and pipeline movement.
To address some of the above-noted operational issues, and perform maintenance on the hydrocarbon fluid pipeline, a pipeline pig may be used. A pipeline pig is a mechanical device sent through the hydrocarbon pipeline to perform a variety of maintenance functions. The most common pig is a scraper pig, which removes wax that precipitates out of the oil and collects on the walls of the hydrocarbon fluid pipeline. As noted above, the colder the hydrocarbon fluid, the more wax buildup. This buildup can cause a variety of problems, so regular “piggings” are needed to keep the pipe clear. However, at reduced flow rates, these piggings may be interrupted, have increased operational issues, or may require additional pigging operations.
Other operational issues may include decreased leak detection. Startup, shutdown, and other safety issues may also increasingly be a concern.
Reliable operation may be established for a specific desired flow rate in barrels per day (BPD). With a reduced flow rate stemming from reduced pressures and supply, it may be desirable to implement mitigation techniques.
While hydrocarbon fluids typically enter the hydrocarbon fluid pipeline from a source, i.e. reservoir, at elevated temperatures, the hydrocarbon fluid may be quickly cooled within the hydrocarbon fluid pipeline. A small number of refineries along the hydrocarbon fluid pipeline may add some heat. However, this heat may not be sufficient to reduce operational issues and reduce cost to effectively maintain the hydrocarbon fluid pipeline. Thus, it may be desirable to further heat the hydrocarbon fluid within the hydrocarbon fluid pipeline.
One approach to heating the hydrocarbon fluid pipeline may include construction of steam injection plants for conduction heating via heat exchangers. However, relatively large temperature deltas are required for conductive heating.
U.S. Patent Application Publication No. 2011/0049133 to Przybyla discloses RF heating of a dielectric fluid within a pipeline. RF power is applied to electrode plates which heat the hydrocarbon fluid passing through pipeline. Unfortunately, the electrode plates obstruct the pipeline flow, and pig operations.
U.S. Pat. No. 6,142,707 to Bass et al. discloses direct electric pipeline heating. Inner and outer conductive walls serve as a path for current flow. The thermal conduction from resistive heating of pipeline walls, however, may be inefficient.
U.S. Patent Application Publication No. 2010/0219105 to White et al., and which is assigned to the assignee of the present invention, discloses RF heating of hydrocarbon fluids in a hydrocarbon fluid pipeline. A tunable radiating antenna is wrapped around a non-conductive pipe to define a radiating element implementation.